CSF Biomarkers of Parkinson Disease (PD) and Related Disorders: We hypothesized that cerebrospinal fluid (CSF) levels of neuronal metabolites of catecholamines would detect central catecholamine deficiency in PD and other alpha-synucleinopathies. In 2012 we reported that synucleinopathies feature CSF neurochemical evidence for central dopamine (DA) and norepinephrine deficiency, that (PD) and pure autonomic failure involve differential dopaminergic vs. noradrenergic lesions, and that CSF 3,4-dihydroxyphenylacetic acid (DOPAC) provides a sensitive clinical laboratory means to identify PD even early in the disease (Goldstein et al., Brain 2012;135:1900-1913). Building on these findings, in the NINDS PDRisk study (see below) we are asking whether people with multiple risk factors for PD also have decreased CSF DOPAC, and we are following such people to determine if low CSF DOPAC predicts later development of PD. Since DOPAC undergoes substantial and individually variable metabolic conversion to homovanillic acid (HVA), we are developing assay methodology for CSF HVA, with the expectation that combined measurement of HVA, DOPAC, and DA will refine CSF biomarkers of central DA deficiency in PD. In collaborative studies with J. Zhang (Univ. of Washington), we have provided CSF samples for proteomic profiling. An elevated ratio of alpha-synuclein phosphorylated at the 129 position (PS-129):total alpha-synuclein may be a biomarker of PD (Wang et al., Science Transl Med 2012;4:121ra20). We are interested in determining if pure autonomic failure, a Lewy body disease in which the patients do not have Parkinsonism, also features increased PS-129:total alpha-synuclein and whether this ratio is related to CSF DOPAC across patients with alpha-synucleinopathy and control subjects. Biomarkers of Risk of PD: We are testing whether people with multiple risk factors for PD have biomarkers of loss of catecholamine neurons in the brain or periphery and if so whether they develop clinical PD during follow-up. Via a unique Protocol-specific website (https://pdrisk.ninds.nih.gov) that has been visited by more than 60,000 people to date, 295 people have been identified with multiple statistical risk factors for PD. We are screening eligible people to confirm their risk factors, admitting them for inpatient biomarkers testing including autonomic function tests, brain 18F-DOPA PET, cardiac 18F-dopamine PET, and CSF catechols, and following them longitudinally over several years. Preliminarily, people with multiple PD risk factors have evidence for decreased baroreflex-cardiovagal gain, CSF DOPAC, and globus pallidus 18F-DOPA-derived radioactivity (unpublished observations). Biomarkers Validation by In Vivo and Post-mortem Neurochemistry: We continue to find that patients with established Parkinson disease (PD) have low values for both the putamen:occipital cortex (PUT:OCC) ratio of 18F-DOPA-derived radioactivity and CSF dihydroxyphenylacetic acid (DOPAC), cross-validating the in vivo neuroimaging and neurochemical approaches. In an ongoing post-mortem study, PD patients have been found to have extremely low putamen contents of both DA and DOPAC (Goldstein et al., J Neurochem 2013 doi: 10.1111/jnc.12345), including a subset of PD patients with low PUT:OCC ratios and CSF DOPAC studied at the NIH. We also recently completed a post-mortem study demonstrating that myocardial norepinephrine (NE) content is decreased by more than 95% in patients with Lewy body diseases compared to controls. From analyses of myocardial levels of catechols, we estimate that in PD there is about a 75% decrease in myocardial sympathetic innervation, coupled with about a 90% decrease in NE storage in the residual nerves. These findings confirm in vivo neuroimaging studies reported by our group since 1997 based on 18F-DA PET scanning and reinforce the view that PD is not only a movement disorder from loss of substantia nigra DA neurons but also is a form of dysautonomia from a profound cardiac sympathetic lesion. 11C-Methylreboxetine PET to Visualize Noradrenergic Innervation: Until recently, no radioligand for neuroimaging had successfully and specifically visualized central neural sites of noradrenergic innervation. 11C-Methylreboxetine (11C-MRB) has these capabilities. In the past year we introduced 11C-MRB PET scanning at the NIH Clinical Center. Preliminarily, 11C-MRB visualizes the sympathetic innervation of the heart, parotid glands, nasopharyngeal mucosa, and choroid plexus; a variety of cortical and subcortical structures known to receive noradrenergic innervation, including the thalamus, medial prefrontal cortex, insula, amygdala, and hippocampus; and brainstem structures including the pontine locus ceruleus, the main source of norepinephrine in the brain. We plan to validate 11C-MRB as a selective ligand for the cell membrane norepinephrine transporter (NET) in humans by examining effects of NET blockade and to apply 11C-MRB to test whether Lewy body diseases are associated with central noradrenergic denervation. Skin Biopsy Biomarkers of Synucleinopathies: In a collaborative study with R. Freeman (Harvard) as a member of the Autonomic Rare Diseases Clinical Research Consortium, we are providing skin biopsy specimens from patients with different forms of alpha-synucleinopathy, to determine whether alpha-synuclein or tyrosine hydroxylase immunostaining can provide pathophysiologically relevant biomarkers.